Flight, April 1926

THE PANDER LIGHT BIPLANE
A School Two-Seater with 45 H.P. Anzani Engine

   AFTER the success which attended the production of the light monoplane with 30 h.p. Anzani engine, which was exhibited at the last Paris Aero Show, and of which several specimens have from time to time visited this country, it is not surprising that Mr. H. Pander of The Hague, should have turned his attention to a two-seater. When we visited the Pander Works last summer we had an opportunity of seeing the sketch design for the two-seater and also some of the parts which were then in course of manufacture at the Pander works. The machine, known as the Type E, has now been finished and was tested recently by Lieutenant Elkerbout of the Dutch Navy. The machine was found to be perfect as regards trim, and during a preliminary test flight the manoevrability was proved to be excellent. Later in the day a number of passengers were given their bapteme de fair in the Pander, among them being Mr. Pander senior, who, although he has been an aviation enthusiast for several years, has not hitherto made a flight, the reason presumably being that hitherto his firm has produced single-seaters only.
   The Pander type E, it will be seen from the accompanying illustrations, is a biplane having a very small lower plane. In other words it is of the type which has come to be described as a sesquiplan, or one-and-a-half plane. An unusual feature of the machine is the type of wing bracing employed. In order to keep the wing weight down, and also to facilitate storage and transport, it was decided not to make the top plane a pure cantilever, but as it was desired to keep the external members of the wing bracing structure down to a minimum a rather unusual form of wing bracing, shown in the illustrations, was evolved. The top plane is built in two halves, pin-jointed at the centre to the cabane legs rising from the top longerons of the fuselage. Each wing half is supported by a pair of inter-plane V-struts, and the lift is taken by a single strut sloping outwards from the top longerons of the fuselage to the foot of the V struts where these meet the lower plane. In normal straightforward flying, therefore, the V-struts are working in tension, and it is only at attitudes causing large movements of the centre of pressure that any of these struts have to resist compression loads. It would appear likely that owing to the relatively flat angles very considerable compression loads may be present in the single sloping lift struts, but doubtless these have been built of sufficiently heavy-gauge, steel tubes to carry the loads imposed upon them and we are informed that the machine has been designed with a factor of safety of 74, so as to be eligible for its aerobatics airworthiness certificate. For the rest the Pander Type E shows very clean lines, and the view from both cockpits should be excellent, except in an upward direction, as the lower plane is of such small chord (2 ft. 9 in.) that it can scarcely obstruct the view from the rear cockpit to any material extent.
   Constructionally the Pander Type E is of composite type, wood being the material used exclusively in the wing construction and also in the rear portion of the fuselage, while the rest of the machine, i.e., front portion of fuselage and the rudder and elevator, are of welded steel tube construction. The upper wing, which has a span of 32 it. 10 in. and a maximum chord of 5 ft. 3 in., is built up on two main spars of box section, with spruce flanges and three-ply walls. The ribs are of three-ply, the top plane being further stiffened by having the whole leading edge, back to some distance aft of the front spar, covered with three-ply. The lower plane, which has a span of 16 ft. 5 in. has a single box spar, which measures 8 in. in width and just over 5 in. in depth. This box spar is built up of spruce and three-ply and the wing is further stiffened by a three-ply covering over the leading edge, forming yet another box spar. The covering of the wings is fabric, except over the centre portion of the top plane, in which are housed the two petrol tanks (each with a capacity of 7 1/2 gallons), which is covered with three-ply. The interplane V-struts and the single lift struts are of streamlined steel tube and the rear strut of the V's has provision for adjustment of its length for the purpose of trueing-up.
   The fuselage, which is of oval cross-section, is built in two halves, of which the front portion is of welded steel tube construction, the bracing being in the form of diagonal tubes as regards the forward panels, but having piano-wire bracing in the side panels in way of the pilot's cockpit. The rear portion of the fuselage is of similar construction to that of the Pander single-seater, i.e., light formers and stringers covered with plywood. The two fuselage portions are joined together at four points, where long fish-plates extend aft from the steel tube longerons to form a joint with the wooden longerons of the rear portion. These fish-plates may be seen in some of the photographs.
   The machine is equipped with dual controls, consisting of the usual joy-stick for elevator and ailerons, but having pedals in place of the more usual foot-bar for the rudder, the pedals being more convenient in a machine in which space, and particularly width, is restricted.
   The 45 h.p. 6-cylinder Anzani engine is attached at four points to the main structure of the fuselage, and a fireproof bulkhead is interposed between the engine and the front cockpit. The whole of the front portion of the fuselage is covered with sheet aluminium. As already mentioned the petrol tanks are carried in the top plane, so that direct gravity feed can be employed, and the petrol system is such that the fuel can be taken from either tank or from both tanks simultaneously.
   The undercarriage is of streamlined steel tubes, with the axle working in a slot in the vertical strut, and anchored in such a way by rubber cord shock-absorbers that not only can it travel up and down but is also free to move to a considerable extent laterally. The front undercarriage strut runs to the top longeron of the fuselage, while the rear strut runs to the lower longeron, the V thus formed being braced laterally, not by cables or streamlined wires as is usually done, but by short steel tube struts, sloping to the centre line of the bottom of the fuselage.
   As in the Pander monoplane, the fin and tail plane are entirely of wood construction, covered with plywood and built into the fuselage. The rudder and elevator have steel tube leading edges and welded sheet-steel ribs. In order to facilitate taxying, the tail skid is mounted on and turns with the rudder, the method of mounting it in the rudder being shown in one of the photographs.
   Following is a brief specification of the Pander type E: Weight empty, 702 lbs.; total loaded weight (pilot, passenger, and 4 hours' fuel). 1,180 lbs.; total wing area, 190 sq. ft.; wing loading, 6-2 lbs./sq. ft.; engine, 45 h.p. Anzani, developing normal power at 1,500 r.p.m., and a maximum of 50 h.p. at 1,580 r.p.m.; power loading (on normal speed), 26-2 lbs./h.p.; maximum speed, 78 m.p.h.; cruising speed, 72 m.p.h.; landing speed, 38 m.p.h.; climb to 3,000 ft. in 7 3/4 mins. Ceiling 11,500 ft.